The death toll from the huge tornado that ripped through Joplin, Mo., has topped 115, and officials say grimly that they expect that number to rise. Suddenly homeless people were finding shelter wherever they could, including in businesses and community centers.

The tornado, the deadliest in the United States in 60 years, spread damage across a six-mile stretch of southwestern Missouri. Emergency services workers reported that about 2,000 buildings were damaged in the city of 50,000, including the house of the city's fire chief. Tornado damage was also reported in Kansas and Minnesota. Fierce tornadoes were also reported in the southeastern U.S. last month.

The number of tornadoes so far in 2011 is 1,168, according to the Center for Severe Weather Research in Boulder, Colo. The center said that the average annual total for the first five months of the year was less than 700. Some meteorologists have speculated that the current La Nina, a Pacific Ocean weather pattern that isn't an annual occurrence, might have contributed to the higher-than-normal number of tornadoes.

Speculation has also gone to climate change, with some scientists pointing to an increase in global temperatures as being a factor in increasing the number of tornadoes, which form when cool air runs up against warm, humid weather. Even though the number of tornadoes has been higher, however, the higher resulting death toll is more a result of population expansion, said other scientists.

The Joplin tornado exacted a particularly high death toll because it hit a hospital. Still, it was nowhere near the deadliest tornado on record. That would be the one that tore through Illinois, Indiana, and Missouri on March 18, 1925, killing 695 people. That was by far the most deadly, with the second-highest death toll occurring in a twister that tore through Natchez, Miss., on May 6, 1840, killing 317 people.

The Joplin tornado currently ranks ninth on the death toll list and is likely to rise. The list, which records single instances, does not include the group of tornadoes that hit the Southeast last month. A total of 346 people died as a result of those.